1. FIELD OF THE INVENTION
The present invention relates to a sealing structure of a pressure container such as an extraction tank which is a main component of the apparatus used for performing, for example, supercritical extraction methods, and which is used under operational pressure as high as 200 to 300 kg/cm.sup.2 G.
2. DESCRIPTION OF PRIOR ART
The applicant invented a pressure container comprising a cylindrical body 2' and two covers 1'a, 1'b which are respectively engaged in the open portions at both ends of the cylindrical body 2', the two covers being combined with each other by means of tie rods 1'c to form a body 1' as one unit which is forwardly pushed out of the cylindrical body 2' by a guide shaft 4' operated by a cylinder 5' so that a sample is discharged from and received in the body 1'. This invention was filed as Japanese Patent Application No. 61-305837 (referred to as the "prior invention").
In the pressure container disclosed in this application, the covers 1'a, 1'b which are respectively tightly engaged in the front and rear open portions of the cylindrical body 2' are combined with each other by the three tie rods 1'c in a state wherein they are opposite to each other at a distance which allows the covers to be simultaneously tightly engaged in the open portions of the cylindrical body 2' through packing 3' provided on the inner surfaces in the front and rear open portions.
Such a container comprising the packings 3' which are provided in the front and rear portions of the cylindrical body 2', however, has the disadvantage that foreign matter contained in the fluid in the cylindrical body 2' adheres to the surface of the packing 3' on the front side and causes damage to the packing 3' and hence deterioration of the sealing performance thereof, as well as a great danger of reducing the life of the packing 3'.
Accordingly, it is an object of the present invention to provide a structure for providing a packing which is capable of resolving the problem involved in the packing 3' disclosed in the prior invention and increasing the life of the packing 3'.